What it is
Lactoferrin is an iron-binding protein of milk and the body's secretions. UniProt's record for the human form (P02788, named lactotransferrin) gives a 710-residue precursor: a 19-residue signal sequence, then the 691-amino-acid glycoprotein, folded and held by 16 disulfide bonds. The cow's-milk form that supplements use (P24627) is 689 residues after its signal sequence.
That makes lactoferrin a protein, more than seventeen times the 40-residue line US regulation draws between peptides and proteins (21 CFR 600.3). It is in this library for two reasons: readers find it on supplement and infant-formula labels beside peptide products, and it carries a peptide inside it.
The peptide is lactoferricin. In 1992 Bellamy and colleagues at Morinaga Milk Industry digested human and bovine lactoferrin with gastric pepsin and isolated a single antibacterial fragment from near the protein's start (Biochim Biophys Acta, PMID 1599934). Its active core is a loop of 18 residues closed by a disulfide bond. UniProt annotates the bovine peptide, lactoferricin B, as 25 amino acids — FKCRRWQWRMKKLGAPSITCVRRAF — and the human one as a longer stretch at the N-terminus. The 1992 paper reports the bovine peptide as the more potent of the two, active against Gram-negative and Gram-positive bacteria at 0.3–3.0 µM in laboratory tests.
What it does in the body
UniProt's function annotation describes lactoferrin as a major iron-binding and multifunctional protein of exocrine fluids such as breast milk and mucosal secretions. Two antimicrobial actions are listed: holding free iron, which bacteria need to grow, and direct damage to bacterial outer membranes, releasing lipopolysaccharide. The same annotation lists weaker or less-established actions — weak antifungal activity, effects on bone cells, interactions with viruses — drawn largely from laboratory studies.
| What is described | Where the evidence comes from |
|---|---|
| Binds iron; slows bacterial growth | Laboratory studies (UniProt annotation) |
| Lactoferricin kills bacteria | Laboratory studies (Bellamy 1992) |
| Prevents infection in very preterm babies | Large human trials — see below |
| Immunity, energy or wellbeing in adults | Not established |
What it is sold for — and what the human trials found
Lactoferrin is sold as a supplement, often from colostrum or whey, and added to some infant formulas, with claims about immunity, gut health and iron. The largest and best-designed human trials tested it in the population where infection is most dangerous — very preterm and very-low-birthweight babies:
| Trial | Infants | Intervention | Main result |
|---|---|---|---|
| ELFIN, UK, 37 hospitals (Lancet 2019, PMID 30635141) | 2,203 | Bovine lactoferrin 150 mg/kg/day vs sucrose to 34 weeks | Late-onset infection 29% vs 31%; risk ratio 0.95 (95% CI 0.86–1.04) — not significant |
| LIFT, Australia and New Zealand, 16 units (Lancet Child Adolesc Health 2020, PMID 32407710) | 1,542 | Bovine lactoferrin 200 mg/kg/day vs none | Death or major morbidity 21% vs 22%; RR 0.95 (0.79–1.14) — not significant |
| Cochrane review (2020, PMID 32232984) | 5,425 in 12 trials | Any dose | Late-onset sepsis RR 0.82 (0.74–0.91), low-certainty; no difference in necrotising enterocolitis or death |
The ELFIN investigators concluded that their data "do not support its routine use" to prevent late-onset infection in very preterm infants. The LIFT authors' own meta-analysis of 13 trials found fewer late-onset infections but no effect on necrotising enterocolitis or death, and called for future trials to use products with demonstrated biological activity. The Cochrane authors flagged publication bias and small, poor-quality studies that may inflate the pooled effect. In short: the two big trials were neutral, and the positive signal comes from pooling smaller ones.
For adult supplement claims — immunity, energy, iron status — this library has not counted the trials, and none of those uses is an established effect. The label doses quoted in the trials above are trial protocols for premature babies, reported as such.
Where it stands
- Food status in the US. FDA's GRAS inventory (read 2026-10-20) lists 15 lactoferrin notices. Seven closed with "FDA has no questions": GRN 67 and 77 (2001), 130 (2003), 464 and 465 (2014) and 669 (2017) for cow's-milk lactoferrin, and GRN 1219 (2025-05-07) and GRN 1284 (2026-03-25) for bovine lactoferrin made by the engineered yeast Komagataella phaffii. The rest were withdrawn at the notifier's request — including two for human lactoferrin produced in rice — or, in one case (GRN 42, 2001), found not to provide a basis for a GRAS determination. A GRAS letter concerns safety for a stated food use; it says nothing about health effects.
- As a medicine: not approved anywhere this library has found.
- Published record: PubMed returns 11,266 records for lactoferrin (300 tagged as randomised controlled trials) and 517 for lactoferricin; ClinicalTrials.gov lists 168 studies with lactoferrin as an intervention (2026-10-20).
Related reading
LL-37 is another of the body's antimicrobial peptides; the peptide-versus-protein entry explains why lactoferrin counts as a protein and lactoferricin as a peptide; what are peptides covers the basics.